Schooner exposed: Motuhaku Island

Locals believe that the Astrolabe kingfish migrate between the two reefs, to the extent that if one is not firing, a foray across to the other will often produce the goods.​

Words & Photos: ​Colin Bertelsen

Softbaits cast under the shadow of the rock were too much of a temptation for snapper. Aggressive kingfish pounced on speed jigs in 70 metres at the other end of the reef system, and 13 marlin were spotted trailing amongst the kahawai schools one day in March.“Yeah right,” you say.

Of course it’s not always like this, but it did happen for me, once. And although to my despair not one marlin could be enticed to take a livie, the next day a local boat caught three!About 15 miles out from Mt Maunganui there lives this rock that stacks up about 10 metres above the waves and has rocky skirts under water, reaching out 300 metres to the north east and open sea. I say ‘lives’ because this rock and its surroundings are literally alive with life. Seabirds and the odd seal co-habit the exposed rock, while fish life below and about is prodigious, right from the ever-present assorted reef dwellers to marauding kingfish and seasonal marlin.Schooner Rock, or Motuhaku Island as it’s named on nautical charts, has been a popular fishing location for many over the years, as the adjacent 80 metre water depth offers pathways for so many fish species. Until recently I had access to the same chart information as everyone else who is used to picking fishbait from under fingernails; information which okay - but you certainly didn’t push your luck by meandering too close to the obvious underwater threats. Much of the positioning required to anchor in a favourable spot involved hope and guesswork - with persistently strong currents and wind adding to the difficulty of getting it right.

But in the foreseeable future this will all change.Through our work we have built and modified a number of craft for hydrographic mapping, a commercial activity that has developed in leaps and bounds in recent years. The advent of powerful multibeam transducers interfaced with very accurate enhanced GPS systems is having the effect of removing the seawater from the ocean and exposing the seabed to the naked eye. This relationship with the hydrographers has allowed me to preview some of the outcomes of the seabed scanning and view many of my favourite fishing spots in what is effectively a 3D birdseye view – and how revealing it has been!

Much impetus was given to multibeam scanning off the waters off Tauranga in the aftermath of the Rena stranding, and I guess having very detailed seabed maps produced as a result is probably the only positive to come out of the incompetence of the particular master who parked his bloody great ship inconveniently on the Astrolabe, one of the Bay’s most eclectic fishing reefs. I understand for instance that there exist charts showing the location of abandoned containers in deepish water nearby that have become highly productive tarakihi spots. I’ve yet to get my hands on these but I’m working on it! There seems to be some distrust in giving such coordinates to fishing scribes - I can’t figure out why.Schooner Rock is only 6nm from the Astrolabe Reef and shares many of its attributes. Locals believe that the Astrolabe kingfish migrate between the two reefs, to the extent that if one is not firing, a foray across to the other will often produce the goods.

The new charts I’ve previewed were produced by a boat sounding a grid path in certain areas that included Motiti, Schooner, Plate Island, Mayor Island and the Mercury Islands. Also adding to this mapping was a trial done by an aircraft. In this instance the plane flew a grid path and scanned the seabed from above, but effectively only down to about 35 metres. This technique certainly has the advantage of covering those prickly shallow areas where hydrographic boats dare not venture but it has yet to be decided if this method can be justified in terms of clarity and possibly cost.I study these charts on a laptop and by scrolling with the mouse can bring up the depth and GPS coordinates of any fishy-looking site within. This ability will become more commonplace as the new charting integrates into the electronic charts you can already download free from the LINZ website (http://www.linz.govt.nz/sea).

Charts like these are mostly produced commercially for private concerns and LINZ (Land Information New Zealand), but some of the manufacturers of marine electronics are already into multibeam scanning, which is allowing individuals to produce their own charts of favourite fishing areas. One example is the WASSP system developed by New Zealand’s Electronic Navigation Ltd. ENL’s WASSP is a multi-award-winning multi-beam system, which produces 3D topographic imagery of the seafloor and associated fish detection. This system has proven very popular with crayfishers but does require an on-board 230V power supply and computer. These sets sold for upwards of $50,000 initially, but they are now closer to $40,000 and it is expected that with competition from other manufacturers and increased production levels, such systems will eventually become financially viable for even the recreational fisher.

Meanwhile some manufacturers are already selling lesser units capable of recording seabed scans for uploading later to home computers. Over time a fisher can build up an excellent seabed map, since each outing can add more data to his home computer file.However, I digress. Let’s look at the professionally-produced chart of Schooner. The rich blue colour coding indicates water of 75-plus metres and the green is around the 50m mark. As you can see, the three areas marked A have almost sheer drop-offs, the favourite haunt of XOS kingfish. Areas C and D are scattered rock formations at 75 metres, areas normally populated by tarakihi. I have pulled tarakihi up 3 at a time from area C and also managed half-a-dozen small hapuku on one trip.Area B represents danger. In heavy swells the top of Keel Rock, as it is known, breaks the surface - and the area F nearby is also shallow enough to swirl and threaten. Once in my gamefishing heyday I trolled across this part of Schooner’s reef system during a moderate swell, totally unaware of the dangers lurking below. Glimpsing a dark shadow alongside the boat I looked behind to see the hard face of an encrusted rock sparkle momentarily in the sunlight. The boat’s stern gear escaped the clutches of the boiling snarling teeth of Keel Rock this time but spitefully, the rock grabbed all five expensive marlin lures that were following and wouldn’t let go. I know at least 3 launches that have suffered drive gear carnage on this aptly-named beast.With little imagination a fisher can visualise straylining possibilities hereabouts where shallow water anchoring is possible with large fish holding areas behind which berley can be streamed. The currents on this reef can be quite strong, which is understandable when a tidal drift in 80 metres suddenly encounters a wall of rock that reaches the surface. These swirling currents, and the up-surging nutrients they release, are the reason so many surface fish in particular amass around the rock. Of course the trevally, maomao and kahawai attract the larger predators ... including marlin in the summer and autumn months.

I was involved with a keen angler around 2002 in trying to capture New Zealand’s first landbased marlin. We put the angler and his mate on the rock by manoeuvring the boat close in on the south-western corner where a depth of 40 metres is enjoyed just a few metres out, passed over the livebaits as needed and stood by, awaiting the action. Over several days the closest we came was when two marlin charged in within metres of the rock, ignoring the livebait offering close by. They scared the daylights out of the swarm of baitfish that were happily dining on my berley trail on the other side of the rock, and then continued on their merry way!All was not lost however, as our intrepid rock hopper pulled in snapper while he was waiting, a feat accomplished by dropping baits almost vertically below his perch and hoping they didn’t fall off as he dangled them up to his chilly bin.

The marlin feat is yet to be achieved as far as I am aware, but I still claim that Schooner Rock offers the best odds for an enthusiast to make a name for him or herself.These new seabed maps, particularly of the Motiti Island environs, have provided me with a bonanza of potential fishing spots where I can partake of my favoured straylining pastime. Fortunately, softbait enthusiasts will also enjoy the same areas and can arm themselves with a multitude of spots to suit all wind directions.

As technology encroaches, the fish seem not to stand a chance, but really, it doesn’t work that way. The new data has to be interpreted correctly for success to ensue, and there will always be days when even the most expert of fishers can’t open a fish’s mouth and put a hook in it. Plus, more fish, especially the kings, are being released and are indeed fighting another day.Meantime, all these extra options offered by multibeam scanners keep fishers interested and optimistic if, unfortunately, somewhat lighter in the wallet department!

​Acknowledgement Land Information New Zealand (LINZ) for use of digital charts